The frequency band denoted Ku corresponds to frequencies between 12 and 18 GHz, or wavelengths between 2.5 and 1.6 cm. The frequency band denoted Ka corresponds to frequencies between 26.5 and 40 GHz or wavelengths between 11.3 and 7.5 mm.
The frequency band denoted Q/V corresponds to frequencies between 33 and 75 GHz or wavelengths between 9.1 and 3.3 mm.
There are a large number of applications involving reflector antennas. Their main aim is to attain high gains by constructing enormous reflectors, which is only possible for radio telescopes on the ground.
For satellites, the gains required are smaller (of the order of 40 to 50 dB), but the main limiting factors are the size and mass to be sent into space. In fact it is not possible to oversize the reflectors to improve the gain.
One of the solutions consists in using the antenna design of the Gregorian type, with two reflectors positioned face to face and making it possible to obtain in a small volume an antenna with a larger equivalent focal length.
For this type of antenna, the reflectors must:                have a diameter between 250 and 1200 mm compatible with a space environment,        exhibit a reflective profile manufactured with very high precision. The manufacturing defect of an active surface can be evaluated from the RMS value. The RMS value is the mean value of the standard deviations between the profile of the manufactured surface and the profile of the desired theoretical surface. Applications in Q/V frequency bands require the attainment of an RMS of the order of 20 microns,        display a high stability for the reflective profile over a wide range of temperatures, from −200° C. to +200° C. This necessitates the use of materials with a low coefficient of thermal expansion.        be stiff, in other words the first resonance mode must be greater than a frequency of 60 Hz for a defined type of antenna.        be of low weight, typically a mass of less than 400 g for a reflector of 500 mm in diameter, for example, and        be easy to implement so as to limit production costs.        
A first conventional technology, so-called “thick shell” technology, is widespread. This technology relies on a so-called “sandwich” structure. A reflector manufactured using this technology comprises two membranes or skins and a spacer corresponding to a structure maintaining a relative position for the membranes and ensuring the stiffness of the “sandwich” structure thus formed. For space applications, the membranes are generally made using carbon reinforcement and the spacer is generally of “honeycomb” or CFRP (Carbon Fibre Reinforced Polymer) type.
This design is especially competitive for reflectors with a diameter between 1 and 2 m. The assembly of this type of structure is, however, too complex and therefore too expensive for reflectors of small diameter.
This technology also requires the use of a large quantity of adhesive, which is not compatible with applications at high temperatures.
Moreover, a reflector of a diameter of 500 mm manufactured using the so-called “thick shell” technology weighs 550 g. This technology does not make it possible to attain the weight targets set for applications in a space environment.
A second so-called “metallic” technology is used for the manufacture of reflectors of small diameter. The reflectors are conventionally produced by machining. This technology is advantageous from an economic point of view.
On the other hand, this technology performs poorly where weight targets are concerned. Indeed, the mass of a main reflector of 500 mm in diameter comprising an alloy of Ta6V type is around 900 g, or more than twice the desired weight targets for space applications.
A third so-called “Isogrid” technology described in Patent Application EP 0948085 performs very well technically.
This product is a reflector comprising a membrane on which is fixed a stiffening lattice. The stiffening lattice is a reinforcement grid forming a so-called “Isogrid” triangular pattern arranged adjacently to the first structure, the stiffening lattice being fixed to the membrane by adhesive bonding.
The complexity of assembly of the reinforcement grid means that this technology does not perform well from an economic point of view for reflectors of small diameter, in the same way as the so-called “thick shell” technology.
A fourth technology, so-called “monolithic technology with peripheral stiffener” makes it possible to overcome the problems related to weight.
This technology comprises a monolithic membrane onto which a peripheral stiffening ring is adhesively bonded. The stiffening ring is a rib comprising carbon, making it possible to stiffen the reflector and thus to attain the resonant frequency targets.
This solution brings an improvement in terms of the weight of the reflector, though the process of assembly and manufacture is not optimized.
Indeed, the production of a reflector using this technology seems to require the production of two separate moulds: a first mould to enable production of the active face of the reflector and a second mould to enable production of the peripheral stiffening ring.
Moreover, the cold-adhesive bonding of the peripheral stiffening ring onto the active face of the reflector limits the range of use temperatures.